The present invention relates to a device for maintaining a load attached to an aircraft.
Military aircraft or those used for military purposes frequently carry external loads, usually arms and especially bombs.
They are carried under the fuselage or under the wings where they are attached to built-on elements called masts or beams.
These masts are rigid structures of elongate form which on the one hand are fastened to the aircraft and on the other hand carry, in their lower part, more or less complex mechanisms intended for attaching the load or loads. Most often, these loads, for example bombs, have in their upper part one or two rings for ensuring their fastening.
The connection to the mast is made as follows:
on the mast there are articulated hooks which take up the rings of the load in order to suspend the latter on the mast,
in order to immobilize the load attached in this way, the latter is clamped firmly on bearing pieces which project on each side of the mast in the vicinity of the hooks.
In fact, during the movement of the aircraft in flight, it is essential that the load should form a single unit with the mast and that the forces which it undergoes do not bring about a relative movement between it and the mast. It is therefore necessary to generate sufficient stresses in the region of the bearings to ensure that the load is effectively immobilized.
Conventionally, the fastening of the load is carried out by means of a mechanical control actuated manually. In contrast, the flight jettisoning mechanism is actuated by means of compressed gases generated either by the combustion of a small powder charge or as a result of the opening of a reserve (for example, compressed-gas bottle). The advantage of the latter solution is that it does not pollute the circuits in which the gas circulates, this being very important to the user for the maintenance of the circuits.
As regards putting the load under stress by means of the pieces provided for this purpose, this can be carried out in various ways:
a movement of the fastening system, the bearings being, stationary pieces,
the use of screws passing through the bearing pieces and coming to bear on the load (called set screws),
movable bearings actuated by means of a specific mechanism.
In these various instances, the maneuver is carried out by means of a mechanism set in motion manually by the use of suitable tools.
The operation of bringing to bear takes place in two stages:
the load is brought into contact with the bearings, without exerting any appreciable force in the region of the bearing zone,
a so-called "prestressing" force is then exerted by applying a torque of given value to the mechanism or by causing the rotary pieces transmitting the torques to execute a specific number of revolutions.
According to patents HOLTROP U.S. Pat. No. 4,441,674 and Hasquenoph, a jack, U.S. Pat. No. 4,168,046, the movable assembly of which is actuated by means of a fluid under pressure, is used in order to carry out the bringing into contact with the bearings and the prestressing.
The disadvantage of this arrangement is that the same member is used for two different operations, the first requiring a low force and a high movement capability and the second requiring a high force for a reduced movement. This results in an excessive weight and cost.
The object of the invention is to provide a device which is simpler and lighter, while at the same time affording the same safety as prior devices.